A microwave dielectric material and its preparation method

Abstract

This invention discloses a microwave dielectric material and its preparation method, relating to the technical field of microwave materials and their preparation methods. The microwave dielectric material is prepared from a microwave raw material main crystalline phase system and a modifier, wherein the main crystalline phase system is (1-z)Ba. 6‑3x (Sm 1‑y Bi y ) 8+2x Ti 18 O 54 -zCaTiO3, where x = 0–1, y = 0–0.4, and z = 0–0.3. This invention utilizes (1–z)Ba 6‑3x (Sm 1‑y Bi y ) 8+2x Ti 18 O 54 -zCaTiO3 is set as the main crystal phase system, through Ba with high dielectric constant. 6‑3x (Sm 1‑y Bi y ) 8+2x Ti 18 O 54 By combining the system with the high dielectric CaTiO3 system, adjusting the content and modification of each component in the main crystalline phase, the resulting dielectric material has the characteristics of high dielectric, low loss, high Q*f value, and small capacity temperature coefficient, and the sintering temperature is 1220℃~1270℃.

Description

Technical Field

[0001] This invention relates to the technical field of microwave materials and their preparation methods, specifically to a microwave dielectric material and its preparation method. Background Technology

[0002] Microwave dielectric materials are a new type of functional material that has developed rapidly in recent decades. They are divided into three categories: low dielectric, intermediate dielectric, and high dielectric. All of them have the characteristics of low dielectric loss and small capacitance temperature coefficient. They are used to make ceramic substrates, resonators, filters, etc., and are widely used in mobile communications, satellite positioning, radar and other fields. With the development of miniaturization, high Q and high stability of microwave components, there is a need for dielectric materials for preparing microwave devices to have high dielectric constant, low dielectric loss, high Q*f value and small temperature change rate. The high dielectric microwave dielectric materials used in the market are generally BaO-Nd2O3-TiO2 systems, and the dielectric constant is generally not more than 100. The widely used high dielectric microwave dielectric materials are BaO-Nd2O3-TiO2 system dielectric materials with a dielectric constant of 90 to 95, such as FERRO's C0G-900 ceramic material. Meanwhile, among the microwave dielectric materials with high dielectric constants reported in existing data, almost all reports only cover their dielectric constant, dielectric loss, and capacity temperature change rate. Reports on their insulation resistance, insulation strength, and Q*f value are scarce, and their applications are not observed, thus failing to realize their engineering application value.

[0003] With the rapid development of mobile communication technology and 5G technology, higher requirements have been placed on the size of microwave devices, requiring small volume and large capacity. Therefore, microwave dielectric materials with dielectric constants below 100 can no longer keep up with the development needs. Among high-frequency dielectric materials, SrTiO3 and CaTiO3 have large dielectric constants and low dielectric losses, but their capacitance temperature change rates are both >1000ppm / ℃, making it difficult to produce microwave dielectric materials with dielectric constants >100 and capacitance temperature change rates that meet C0G characteristics.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The technical problem to be solved by this invention is that current microwave dielectric materials are greatly affected by temperature and have low dielectric constants.

[0006] This invention is achieved through the following technical solution:

[0007] This application discloses a microwave dielectric material prepared from a microwave raw material main crystalline phase system and a modifier, wherein the main crystalline phase system is (1-z)Ba. 6-3x (Sm 1-y Bi y ) (8+2x) Ti 18 O54 -zCaTiO3, where x = 0 to 1, y = 0 to 0.4, and z = 0 to 0.3.

[0008] Preferably, the modifier includes La2O3, SrCO3, Nb2O5, and CaSiO3;

[0009] The weight fraction of La2O3 in the microwave raw material is 0.2wt% to 2wt%, the weight fraction of SrCO3 in the microwave raw material is 0.1wt% to 3.5wt%, the weight fraction of Nb2O5 in the microwave raw material is 0.15wt% to 1.0wt%, and the weight fraction of CaSiO3 in the microwave raw material is 0.1wt% to 3wt%.

[0010] Preferably, x = 0.1–0.25, y = 0.15–0.25, z = 0.05–0.1, and the weight fraction of La2O3 in the microwave raw material is 0.5 wt%–1.6 wt%, SrCO3 is 0.6 wt%–2 wt%, Nb2O5 is 0.12 wt%–0.2 wt%, and CaSiO3 is 0.2 wt%–0.35 wt%.

[0011] To achieve the above objectives, this application also proposes a method for preparing a microwave dielectric material, comprising the following steps:

[0012] S1: Weigh BaCO3, Sm2O3, Bi2O3, TiO2, and CaCO3 according to the dosage of the main crystalline phase system, and then mix, grind, dry, sieve, granulate, and calcine them in sequence to obtain the main crystalline phase system material;

[0013] S2: Weigh the main crystalline phase system material and the modifier, and then mix, grind, dry and sieve them in sequence to obtain the microwave dielectric material.

[0014] Preferably, the CaSiO3 is prepared by weighing CaCO3 and SiO2 according to the molecular formula, and then mixing, grinding, drying, sieving and calcining them in sequence.

[0015] Preferably, the grinding method in S1 includes ball milling for (5-7) hours using deionized water as the medium and in a weight ratio of material:ball:water of 1:(4-7):2.

[0016] Preferably, the granulation method in S1 includes adding deionized water for granulation, and the calcination temperature in S1 is 1180℃±10℃, and the calcination time is (2.5~3.5) hours.

[0017] Preferably, the grinding method in S2 includes ball milling for 33 to 48 hours at a weight ratio of material:ball:water of 1:5:(0.9 to 1.5).

[0018] Preferably, the calcination temperature during the preparation of CaSiO3 is 1280℃±10℃.

[0019] Preferably, the process further includes step S3: granulating, pressing, and sintering the microwave dielectric material prepared in step S2 to obtain a dielectric material disc, wherein the sintering temperature is 1220℃~1270℃.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) This application (1-z)Ba 6-3x (Sm 1-y Bi y ) 8+2x Ti 18 O 54 -zCaTiO3 is the main crystal phase system, through Ba with high dielectric constant. 6-3x (Sm 1-y Bi y ) 8+2x Ti 18 O 54 By combining the system with a high dielectric CaTiO3 system, adjusting the content and modification of each component in the main crystalline phase, the dielectric material of this invention has the characteristics of high dielectric, low loss, high Q*f value, and small capacity temperature coefficient, and the sintering temperature is 1220℃~1270℃.

[0022] (2) This invention uses (1-z)Ba 6-3x (Sm 1-y Bi y ) 8+2x Ti 18 O 54 By adjusting the proportions of elements in the -zCaTiO3 composite main crystalline phase, a sintered block material with high dielectric constant, low loss, and low capacity temperature change rate was obtained. Further addition of modifiers to the sintered block further reduced dielectric loss, optimized the Q*f value, and simultaneously improved insulation resistance and insulation strength, resulting in a material with a dielectric constant >110 and a dielectric loss <5.0×10⁻⁶. -4 Microwave dielectric materials with Q*f value > 9000 (1.9GHz) and low capacitance change rate.

[0023] (3) The preparation process is simple and mature, suitable for mass production. The ceramic substrate prepared by the dielectric material of this invention has a dielectric loss of ≤4.0×10⁻⁶. -4 The capacity temperature coefficient is (0±30)ppm / ℃, and the insulation strength is >46kV / mm. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0025] Figure 1 The image shows the XRD pattern of the dielectric material prepared in Example 2.

[0026] Figure 2 This is a SEM image of the substrate surface obtained from the preparation of the dielectric material in Example 2;

[0027] Figure 3 This is a SEM image of the cross-section of the substrate prepared by the dielectric material in Example 2. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] This invention provides a method for preparing a microwave dielectric material, comprising the following steps:

[0032] S1: BaCO3, Sm2O3, Bi2O3, TiO2, and CaCO3 were weighed according to the dosage of the main crystalline phase system, and then sequentially mixed, ground, dried, sieved, granulated, and calcined to obtain the main crystalline phase system material. The grinding method included ball milling for (5-7) hours using deionized water as the medium at a material:ball:water weight ratio of 1:(4-7):2. The granulation method included adding deionized water for granulation. The calcination temperature was (1180±10)℃, and the calcination time was (2.5-3.5) hours. The main crystalline phase system was (1-z)Ba 6-3x (Sm 1-y Bi y ) (8+2x) Ti 18 O 54 -zCaTiO3, where x = 0 to 1, y = 0 to 0.4, and z = 0 to 0.3;

[0033] The modifiers include the following substances in weight percentages (percentage of microwave raw materials): 0.2wt% to 2wt% La2O3, 0.1wt% to 3.5wt% SrCO3, 0.15wt% to 1.0wt% Nb2O5 and 0.1wt% to 3wt% CaSiO3;

[0034] S2: Weigh the main crystalline phase system material and modifier, and then mix, grind, dry and sieve them in sequence to obtain microwave dielectric material. The grinding method includes ball milling for (33-48) hours according to the weight ratio of material:ball:water of 1:5:(0.9-1.5).

[0035] It should be noted that the CaSiO3 is prepared by weighing CaCO3 and SiO2 according to the molecular formula, mixing and grinding them in sequence, drying them, sieving them, and calcining them. The calcination temperature during the preparation of CaSiO3 is (1280±10)℃.

[0036] Comparative Example 1

[0037] A method for preparing a microwave dielectric material is provided, comprising the following steps:

[0038] S1: BaCO3, Sm2O3, Bi2O3, TiO2, and CaCO3 were weighed according to the dosage of the main crystalline phase system, and then sequentially mixed, ground, dried, sieved, granulated, and calcined to obtain the main crystalline phase system material. The grinding method included ball milling for 6 hours using deionized water as the medium at a material:ball:water weight ratio of 1:5:2. The granulation method included adding deionized water for granulation. The calcination temperature was 1180℃, and the calcination time was 3 hours. The main crystalline phase system is (1-z)Ba 6-3x (Sm 1- y Biy ) (8+2x) Ti 18 O 54 -zCaTiO3, where x = 1.2, y = 0.2, z = 0.35;

[0039] The modifier comprises the following substances in weight percentage (percentage of microwave raw material): 1.2 wt% La2O3, 1 wt% SrCO3, 0.3 wt% Nb2O5 and 0.2 wt% CaSiO3;

[0040] S2: Weigh the main crystalline phase system material and the modifier, and then mix, grind, dry and sieve them in sequence to obtain microwave dielectric material. The grinding method includes ball milling for 40 hours according to the weight ratio of material:ball:water of 1:5:1.

[0041] It should be noted that the CaSiO3 is prepared by weighing CaCO3 and SiO2 according to the molecular formula, mixing and grinding them in sequence, drying them, sieving them, and calcining them. The calcination temperature during the preparation of CaSiO3 is 1280℃.

[0042] The differences between Examples 1 to 8 and Comparative Example 1 are the different values ​​of x, y, and z, as well as the different amounts of La2O3, SrCO3, Nb2O5, and CaSiO3, as shown in Table 1 below:

[0043] Table 1. Parameters of the medium material

[0044]

[0045] Experimental results

[0046] The dielectric materials prepared in Comparative Example 1 and Examples 1-8 were granulated using PVA, pressed into discs, and then heated to 500°C at a rate of 2°C / min and held for 2 hours. The adhesive was then removed, and the temperature was further increased to 1220°C–1270°C at a rate of 4°C / min for 3–6 hours to produce disc capacitors. The electrical performance of the disc capacitors was tested. The dielectric constant and dielectric loss of the discs were tested using an impedance analyzer, and the capacitance temperature change rate was tested using a high and low temperature chamber. The insulation resistance and insulation strength of the products were tested using an insulation resistance meter and a withstand voltage meter. The Q*f value of the products at 1.9 GHz was tested using a network analyzer according to the open resonant cavity method. The results are shown in Table 2 below.

[0047] Table 2 Performance Test of Circular Wafers

[0048]

[0049] The dielectric material prepared in Example 2 was used to prepare substrates with dimensions of 40×40×0.12mm, 40×40×0.15mm, and 40×40×0.20mm. Figure 1 The XRD pattern of the dielectric material prepared by the method in Example 2 is shown. Analysis was performed using Jade 6.5. Figure 1 It can be seen that the main crystalline phase synthesized by calcination is Ba. 3.8 Sm 9.4 Ti 18 O 54 Standard PDF card comparison did not detect free Ca. 2+ Bi 3+ The diffraction peaks of ions, as well as CaO and Bi2O3, indicate that after calcination, Ca... 2+ and Bi 3+ It has entered the lattice position and is a typical Ba-Ti-Sm microwave dielectric material. SEM images of the substrate surface and cross-section after sintering at 1250℃ are shown below. Figure 2-3 As shown, by Figure 2-3 It can be seen that after sintering, the ceramic grains are elongated and overlapping, with few pores and a dense structure. The substrate was tested using the same method as the wafer test, and the results are shown in Table 3 below:

[0050] Table 3 Substrate Performance

[0051]

[0052] As shown in Tables 2 and 3, this invention obtains a main sintered block material with high dielectric constant, low loss, and low capacity temperature change rate by adjusting the proportion of each element in the main crystalline phase. Furthermore, adding a modifier to the sintered block further reduces dielectric loss, optimizes the Q*f value, and simultaneously improves insulation resistance and insulation strength, resulting in a material with a dielectric constant >110 and a dielectric loss <5.0×10⁻⁶. -4 Microwave dielectric materials with Q*f values ​​> 9000 (1.9 GHz) and low capacitance change rate were selected. Ceramic substrates with thicknesses of 0.12 mm, 0.15 mm, and 0.20 mm were prepared using a casting process involving casting, lamination, isostatic pressing, dicing, and sintering. Testing showed that their dielectric loss was ≤ 4.0 × 10⁻⁶. -4 The capacity temperature coefficient meets (0±100)ppm / ℃, the insulation strength is >46kV / mm, and the insulation resistance is ≥100×10 11 Ω, dielectric strength ≥45kV / mm, wherein, as shown in Examples 1 and 2, when x = 0.1–0.25, y = 0.15–0.25, z = 0.05–0.1, the weight fraction of La2O3 in the microwave raw material is 0.5wt%–16wt%, and the weight fraction of SrCO3 in the microwave raw material is 0.6wt%.

[0053] When the weight fraction of Nb2O5 in the microwave raw material is 0.12wt% to 0.2wt%, and the weight fraction of CaSiO3 in the microwave raw material is 0.2wt% to 0.35wt%, the capacity temperature coefficient meets the requirement of (0±30)ppm / ℃, and the capacity temperature coefficient conforms to the COG characteristics.

[0054] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A microwave dielectric material, characterized in that, It is prepared from microwave raw material main crystal phase system material and modifier, wherein the main crystal phase system is (1-z)Ba 6-3x (Sm) 1-y Bi y ) （8+2x） Ti 18 O 54 -zCaTiO3, where 0 < x ≤ 1, 0 < y ≤ 0.4, and 0 < z ≤ 0.3; The modifiers include La2O3, SrCO3, Nb2O5 and CaSiO3; The weight fraction of La2O3 in the microwave raw material is 0.2wt% to 2wt%, the weight fraction of SrCO3 in the microwave raw material is 0.1wt% to 3.5wt%, the weight fraction of Nb2O5 in the microwave raw material is 0.15wt% to 1.0wt%, and the weight fraction of CaSiO3 in the microwave raw material is 0.1wt% to 3wt%.

2. The microwave dielectric material according to claim 1, characterized in that, The values ​​are x = 0.1~0.25, y = 0.15~0.25, and z = 0.05~0.

1. The weight fraction of La2O3 in the microwave raw material is 0.5wt%~1.6wt%, the weight fraction of SrCO3 in the microwave raw material is 0.6wt%~2wt%, the weight fraction of Nb2O5 in the microwave raw material is 0.12wt%~0.2wt%, and the weight fraction of CaSiO3 in the microwave raw material is 0.2wt%~0.35wt%.

3. A method for preparing a microwave dielectric material according to any one of claims 1-2, characterized in that, Includes the following steps: S1: Weigh BaCO3, Sm2O3, Bi2O3, TiO2, and CaCO3 according to the dosage of the main crystalline phase system, and then mix, grind, dry, sieve, granulate, and calcine them in sequence to obtain the main crystalline phase system material; S2: Weigh the main crystalline phase system material and the modifier, and then mix, grind, dry and sieve them in sequence to obtain the microwave dielectric material.

4. The method for preparing a microwave dielectric material according to claim 3, characterized in that, The CaSiO3 is prepared by weighing CaCO3 and SiO2 according to the molecular formula, and then mixing, grinding, drying, sieving and calcining them in sequence.

5. The method for preparing a microwave dielectric material according to claim 3, characterized in that, The grinding method in S1 includes ball milling for 5 to 7 hours using deionized water as the medium and a material:ball:water weight ratio of 1:(4~7):

2.

6. The method for preparing a microwave dielectric material according to claim 3, characterized in that, The granulation method in S1 includes adding deionized water for granulation. The calcination temperature in S1 is (1180±10)℃ and the calcination time is (2.5~3.5) hours.

7. The method for preparing a microwave dielectric material according to claim 3, characterized in that, The grinding method in S2 includes ball milling for (33~48) hours at a weight ratio of material:ball:water of 1:5:(0.9~1.5).

8. The method for preparing a microwave dielectric material according to claim 4, characterized in that, The calcination temperature during the preparation of CaSiO3 is (1280±10)℃.

9. The method for preparing a microwave dielectric material according to claim 3, characterized in that, It also includes S3: the microwave dielectric material prepared in S2 is granulated, pressed and sintered in sequence to obtain dielectric material discs, wherein the sintering temperature is 1220℃~1270℃.

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